the pustules of variola and in vaccine lymph has been reported by several investigators: Guarnieri (1892), Monti (1894), Piana and Galli-Valerio (1894), L. Pfeiifer (1894), Clarke (1895), von Sicherer (1895), E. Pfeiffer (1895). Guarnieri in 1892 published a paper in which he claimed to have cultivated the amœboid micro-organism found by him in vaccine lymph by successive inoculations in the cornea of rabbits. E. Pfeiffer has since (1895) confirmed this observation, and has seen the parasite undergoing amœboid movements and in progress of multiplication by spontaneous fission. During the past two years investigations relating to the ætiology of vaccinia and variola have been made at the Army Medical Museum in Washington, by Major Walter Reed, surgeon United States Army. These investigations show that in vaccinated monkeys and in children an amœboid parasite makes its appearance in the blood on the sixth or seventh day after vaccination, and may be found during a period of from five to seven days, when it disappears. Reed has found the same parasite in the blood of patients with variola and in his own blood after an accidental vaccination in the finger. The parasites are not numerous. They are less than a third the diameter of a red blood-corpuscle, and may be observed to undergo amœboid movements in a drop of blood, properly mounted for microscopical examination, during a period of twenty-four hours or more. These amœboid bodies, like the malarial parasite, would be easily overlooked by one not an expert in blood examinations.
The presence of a ciliated amœboid micro-organism in the mucous secretion coughed up by children suffering from whooping-cough has recently been reported by Deichler and confirmed by Kourlow. This may prove to be the cause of the disease, but further researches will, of course, have to be made before this can be determined. In view of the extended investigations made during the past few years by competent bacteriologists, it seems probable that in most of those infectious diseases in which the specific infectious agent has not yet been discovered it belongs to some other class of micro-organisms than the bacteria; and it seems not improbable that some of them at least will prove to be due to infection by "germs" belonging to the class to which your attention has been invited in the present address—viz., the pathogenic protozoa.
